Generally, perfluoropolyether group-containing compounds have very small surface energy and, accordingly, have unique properties such as water- and oil-repellency, chemical resistance, lubricating property, demoldability, and stain resistance. Therefore, they find applications, on account of such properties, as water- and oil-repelling, stain-proofing agents in paper and fiber; lubricating agents in magnetic recording media; oil proof agents in precision machinery; mold release agents; cosmetics; and protecting films. However, the low surface energy of the perfluoropolyether group-containing compounds result in very poor compatibility and affinity with materials such as organic solvents, paints, cosmetics and various coating materials. Therefore, it has been pointed out that where a perfluoropolyether group-containing compound is added to various industrial materials to provide the afore-mentioned properties, problems arise, for instance, in dispersion stability and, therefore, the application of the perfluoropolyether group-containing compounds is difficult.
Also polysiloxanes, i.e., silicone, have a small surface energy and, therefore, have properties such as water-repellency, lubricating property, and demoldability. However, polysiloxanes have a better affinity with materials such as organic solvents, paints, cosmetics, and various coating materials than the perfluoropolyethers. Their dispersion stability can be enhanced by various modifications. Therefore, polysiloxanes can be added to various industrial materials to provide the materials with characteristics of silicone. Thus they are used as an additive to improve performance in various fields. A perfluoropolyether-modified polysiloxane is synthesized as a compound having both of a perfluoropolyether group and a polysiloxane chain (Patent Literatures 1 to 5).
Various defoaming agents are conventionally used in industrial processes where foaming occurs. Inter alia, defoaming silicone agents are widely used, such as oil compounds, comprising a silicone oil such as dimethylpolysiloxane, methylphenylpolysiloxane and methylvinylpolysiloxane, and fine powder of silica; and an emulsion of these oil compounds dispersed in water with a surfactant, because the defoaming silicone agents show various good natures such as better chemical stability and effects even in a smaller amount than the other defoaming agents.
Although these defoaming silicone agents attain the good defoaming effect in aqueous systems, they show an extremely small defoaming effect in organic solvent systems which have a lower surface tension and greater solubility for silicone than in aqueous systems. Japanese Patent Publication No. Sho-35-12564 describes the use of particularly highly viscous dimethylpolysiloxane for a defoaming agent for organic solvent systems, but the defoaming effects are not always satisfactory. Japanese Patent Application Laid-Open Nos. Sho-59-22611 and Sho-60-22907 describe a defoaming agent comprising a perfluoroether as an effective component. Japanese Patent Publication No. Sho-35-12564 and U.S. Pat. No. 4,329,528 describe a defoaming agent for organic solvents comprising a perfluoroalkyl group-containing siloxane as an effective component. Japanese Patent Application Laid-Open No. Hei-2-51644 describes a defoaming agent for organic solvent comprising a perfluoroether group-containing siloxane as an effective component. None of these defoaming agents is well satisfactory. Therefore, a defoaming silicone agent is desired which has a good defoaming effect for organic solvent systems. (See the following Patent Literatures 4 to 8).